Hi,
On 7 Apr 2009, at 19:40, Regina wrote:
> Dear all,
>
> I am relatively new to setting up analyzes on fsl, and would highly
> appreciate your advice on the following, which after searching in the
> documentation I could not find the answer to in a definite way:
>
> 1) If one wishes to censor motion in fsl, by including the time points
> associated with motion as a text file/ EV (explanatory variable) at
> the
> individual level analyzes, should one *orthogonalize* that motion-
> related EV
> in relation to the others? (by looking at the latest fsl practical
> materials, the answer seems to be yes. . . ).
No, you should just leave it as it is; see the brief para in the
manual on head motion parameters at:
http://fsl.fmrib.ox.ac.uk/fsl/feat5/detail.html#stats
> Also, I am currently giving it
> a weight of "1"- as the other EVs typically have- I haven't been
> able to
> find much information on this- should I be doing anything different?
Do you mean in the contrasts? No, this EV shouldn't appear in the
contrasts.
> 2) Could you direct me to a concrete example of the different
> between a real
> and original EV? I understand what the original EVs are.
An "original" EV would be a main effect such as visual stimulation. If
you turn on the temporal derivative then the original EV corresponds
to real-EV-1 (the main effect) and real-EV-2 (its temporal derivative).
Cheers.
>
> Thanks very much!
>
> Regina
>
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Stephen M. Smith, Professor of Biomedical Engineering
Associate Director, Oxford University FMRIB Centre
FMRIB, JR Hospital, Headington, Oxford OX3 9DU, UK
+44 (0) 1865 222726 (fax 222717)
[log in to unmask] http://www.fmrib.ox.ac.uk/~steve
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